Question

In a hydraulic jack as shown, mass of the car is $W=800\text{kg},A_1=10{\text{cm}}^2,A_2=10{\text{m}}^2$. The minimum force $F$ required to lift the car is: [Take $g=10{\text{m/s}}^2$]

• A. $1\text{N}$
• B. $0.8\text{N}$
• C. $8\text{N}$
• D. $16\text{N}$

Answer 1

The correct option is B $0.8\text{N}$

Given,
$A_1=10{\text{cm}}^2$
$A_2=10{\text{m}}^2={10}^5{\text{cm}}^2$
$F_2=Wg=8000\text{N}$

Pressure in the same liquid at the same level should be the same, so we can say that pressure at both the pistons are equal.
$\frac{F_1}{A_1}=\frac{F_2}{A_2}$
By substituting values,
$\frac{F}{10}=\frac{8000}{{10}^5}$
or $F=0.8\text{N}$